JP6901213B2 - Liquid level shape measuring device and method for propellant tank - Google Patents

Description

The present invention relates to a propellant tank of a spacecraft, and more particularly to a liquid level shape measuring device and a method of the propellant tank.

A spacecraft using a liquid propellant (for example, a liquid rocket or an artificial satellite) has a propellant tank that holds the liquid propellant inside, and uses the liquid propellant to perform flight or attitude control.
In this case, the liquid propellant is, for example, a liquid fuel, a liquid oxidant, a compound or mixture of a liquid fuel and a liquid oxidant.

When a spacecraft flies in zero gravity space, the liquid propellant in the propellant tank behaves differently than under gravity. Therefore, a means for detecting the amount of propellant in the propellant tank is required.
The means for detecting the amount of propellant in the propellant tank are disclosed in, for example, Patent Documents 1 and 2.

The "method for measuring the amount of fuel in the fuel tank of a spacecraft" in Patent Document 1 is a measuring method for measuring the amount of fuel in the fuel tank during the acceleration stroke of an artificial satellite. This method is in a tube having a first end connected to a first region constituting the bottom of the fuel tank with respect to the acceleration direction and a second end connected to a second region spaced from the first region. Detect fuel level.

However, the method of Patent Document 1 cannot measure the amount of fuel in a flight state other than the acceleration stroke or when the acceleration direction changes.

Japanese Unexamined Patent Publication No. 9-21674 JP-A-61-122512

FIG. 1 is an explanatory diagram of the method of Patent Document 2.
In the "method for measuring the remaining amount of propellant in a spacecraft" of Patent Document 2, an ultrasonic probe 2 is attached to the surface of a propellant tank 1 mounted on the spacecraft, and the propellant is propelled by the ultrasonic probe 2. The propellant thickness h in the tank is measured, and the propellant amount is measured from this propellant thickness h.
In FIG. 1, 3 is a liquid propellant, 4 is an internal gas, and 3a is a propellant liquid level.

In the method of Patent Document 2, the ultrasonic probe 2 that transmits the ultrasonic wave 5 (transmitted wave 5a) receives the ultrasonic wave 5 (reflected wave 5b) reflected by the propellant liquid surface 3a, and the time difference is T. The propellant thickness h is calculated from the sound velocity C in the propellant.
However, this method has the following problems.

(1) The ultrasonic wave 5 in the liquid propellant is almost totally reflected at the propellant liquid surface 3a. However, in a zero gravity state or a state in which the acceleration direction changes, the liquid level shape changes to various shapes.
Therefore, as shown by points a to d in FIG. 1, if the liquid level shape with respect to the transmitted wave 5a is not within the appropriate range, the intensity of the reflected wave 5b reflected toward the ultrasonic probe 2 is weak and cannot be detected. is there.

(2) It is important for the spacecraft to accurately grasp the remaining amount of liquid propellant (remaining amount of propellant) for the final mission (for example, when leaving orbit and returning to the earth). ..
However, in the case of the method of Patent Document 2, when the propellant thickness h becomes small as shown in points e to g of FIG. 1, the time difference T between the transmission of the transmitted wave 5a and the reception of the reflected wave 5b becomes extremely short. Due to the noise, it becomes difficult to measure the time difference T, and it becomes impossible to accurately measure the remaining amount of the propellant.

Therefore, with the conventional method, it is difficult or impossible to measure the amount of propellant in a weightless state, a state in which the acceleration direction changes, and a state in which the remaining amount of propellant is small.

The present invention has been devised to solve the above-mentioned problems. That is, an object of the present invention is a liquid level shape measuring device and method for a propellant tank capable of accurately measuring the propellant amount in a weightless state, a state in which the acceleration direction changes, and a state in which the propellant amount is low. To provide.

According to the present invention, it is a liquid level shape measuring device for a propellant tank that holds a liquid propellant inside.
A plurality of liquids on the propellant liquid surface due to a plurality of time differences between a probe complex fixed to the outer surface of the propellant tank and a plurality of time differences from the transmission of ultrasonic waves by the probe complex to the reception of the reflected wave of the ultrasonic waves. Equipped with an arithmetic unit that detects the surface position,
The probe complex includes a transmission probe that emits ultrasonic waves and a transmission probe that emits ultrasonic waves.
Provided is a liquid level shape measuring device for a propellant tank, which comprises a plurality of receiving probes that surround the transmitting probe and are fixed to each other at a distance from each other to receive the reflected wave.

Further, according to the present invention, there is a method for measuring the liquid level shape of a propellant tank using the above liquid level shape measuring device.
(A) A plurality of the probe complexes are fixed to the outer surface of the propellant tank at intervals from each other.
(B) Using the plurality of reflected waves received by the plurality of receiving probes of each probe complex, a plurality of liquid level positions on the propellant liquid surface are detected.
(C) Provided is a method for measuring the liquid level shape of a propellant tank, which calculates the shape of the propellant liquid level having a plurality of the liquid level positions.

According to the present invention, a plurality of receiving probes surround the transmitting probe and are fixed to the outer surface of the propellant tank at intervals from each other to receive the reflected wave.
With this configuration, the receiving probe is located away from the transmitting probe, and even if the propellant thickness is small, the time difference between the transmission of ultrasonic waves and the reception of reflected waves is large, reducing the influence of noise. This makes it easier to measure the time difference.

Further, since a plurality of receiving probes receive a plurality of reflected waves, the reflected positions of the reflected waves on the propellant liquid surface are different. With this configuration, even when the liquid surface shape fluctuates to various shapes, one of the reflected waves can be detected by a plurality of receiving probes.

Therefore, according to the present invention, the propellant amount can be accurately measured in a weightless state, a state in which the acceleration direction changes, and a state in which the propellant remaining amount is small.

It is explanatory drawing of the method of Patent Document 2. It is an overall block diagram of the liquid level shape measuring apparatus by this invention. FIG. 2 is a partially enlarged view of FIG. 2 and a sectional view thereof taken along the line BB. It is an operation explanatory diagram of the probe complex. It is explanatory drawing of the liquid level shape measuring method of the propellant tank by this invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to common parts in each figure, and duplicate description is omitted.

FIG. 2 is an overall configuration diagram of the liquid level shape measuring device 100 according to the present invention.
In this figure, the liquid level shape measuring device 100 includes a probe complex 10 and an arithmetic unit 20.

The probe complex 10 is fixed to the outer surface 1a of the propellant tank 1 that holds the liquid propellant 3 inside. In this figure, the propellant tank 1 is spherical, and six probe complexes 10 are fixed to the outer surface 1a of the propellant tank 1 evenly spaced apart from each other.
The propellant tank 1 is not limited to a spherical shape, and may have other shapes. Further, the probe complex 10 is not limited to 6, and may be 1 to 5, or 7 or more.

The computing device 20 is, for example, a computer (PC), receives the transmitted wave 5a of the ultrasonic wave 5 and the reflected wave 5b from the probe complex 10, and superimposes from the transmission of the ultrasonic wave by the probe complex 10. A plurality of liquid level positions of a plurality of propellant liquid levels 3a are detected by a plurality of time differences T until the reflected wave 5b of the ultrasonic wave 5 is received.

FIG. 3 is a partially enlarged view of FIG. 2 and a sectional view thereof taken along the line BB.
In this figure, the probe complex 10 has a transmitting probe 12 that emits an ultrasonic wave 5 (transmitting wave 5a) and a plurality of receiving probes 14 (16 in this example).

The transmission probe 12 is preferably a piezoelectric element, and transmits ultrasonic waves 5 (transmitted wave 5a) by electric pulses. The transmit probe 12 is a vertical probe in this example.

The plurality of receiving probes 14 surround the transmitting probe 12 and are fixed at a distance from each other to receive the reflected wave 5b.
The reception probe 14 is preferably a piezoelectric element, and converts ultrasonic waves 5 (reflected waves 5b) into electrical signals for reception. The receiving probe 14 is a vertical probe in this example.

In this example, the eight inner receiving probes 14 (hereinafter, “inner receiving probe 14A”) are arranged on the same circumference from the center of the transmitting probe 12 at intervals of 45 degrees in the circumferential direction. Has been done. Further, the eight outer receiving probes 14 (hereinafter, “outer receiving probe 14B”) are also circumferentially oriented from the center of the transmitting probe 12 on the same outer circumference of the inner receiving probe 14A. They are arranged at intervals of 45 degrees.
The number of reception probes 14 is not limited to 16, and may be a plurality. Further, the arrangement of the plurality of receiving probes 14 is not limited to this example, and it is sufficient that the transmitting probes 12 are surrounded and spaced apart from each other.

In FIG. 3, the probe complex 10 further has a plurality of wedge members 16.
The plurality of wedge members 16 are sandwiched between the outer surface 1a of the propellant tank 1 and the receiving probe 14, and have a shape corresponding to the traveling path of the ultrasonic wave 5.

FIG. 4 is an explanatory diagram of the operation of the probe complex 10.
In this figure, hm is the planned propellant thickness.
The planned propellant thickness hm is the propellant thickness when the propellant liquid level 3a is close to the transmission probe 12. The planned propellant thickness hm is set so that the remaining amount of propellant can be accurately grasped for the final mission of the spacecraft (for example, when leaving the orbit and returning to the earth).

That is, the planned propellant thickness hm means the "detectable minimum value of the propellant thickness" for accurately measuring the remaining amount of propellant for leaving the orbit. It is preferable that the propellant thickness can be detected even when the propellant thickness is smaller than the planned propellant thickness hm. However, in this case, the measurement accuracy may be lowered or the measurement may not be possible.

In FIG. 4, θ1 and θ3 are angles of incidence of the reflected wave 5b on the wedge member 16 when the planned propellant thickness is hm. The incident angle θ1 is an angle formed by the reflected wave 5b on the wedge member 16 of the inner receiving probe 14A and the perpendicular line of the outer surface 1a. Similarly, the incident angle θ3 is an angle formed by the reflected wave 5b on the wedge member 16 of the outer receiving probe 14B and the perpendicular line of the outer surface 1a.

In FIG. 4, θ2 and θ4 are angles formed by the axial lines of the inner receiving probe 14A and the outer receiving probe 14B and the perpendicular lines of the outer surface 1a.

The wedge member 16 is sandwiched between the outer surface 1a of the propellant tank 1 and the receiving probe 14, and has a function of transmitting the reflected wave 5b incident on the inner surface of the wedge member 16 to the receiving probe 14.
Further, the wedge member 16 has a function of converting the incident angles θ1 and θ3 of the reflected wave 5b described above into refraction angles (for example, θ2 and θ4) suitable for the receiving probe 14.
The relationship between the angle of incidence and the angle of refraction can be determined by Snell's law based on the speed of sound of the propellant tank 1 and the wedge member 16.

The transmission probe 12 has an effective directivity angle φ with respect to the sound axis of the transmitted ultrasonic wave 5 (transmitted wave 5a).
In the present invention, the effective directivity angle φ is preferably set large, for example, 30 to 60 degrees.
In the receiving probe 14 (inner receiving probe 14A and outer receiving probe 14B), the propellant liquid level 3a approaches the transmitting probe 12 with a predetermined propellant thickness (planned propellant thickness hm). At that time, it is located at a position where the reflected wave 5b can be received.

That is, in this example, when the planned propellant thickness is hm, the outer receiving probe 14B is arranged at a position where the reflected wave 5b of the ultrasonic wave 5 having an effective directivity angle φ can be received.
The effective directivity angle φ is usually fixed, but any outer receiving probe 14B can be used regardless of the angle at which the reflected wave returns in response to an unpredictable change in liquid level shape. It is better to set so that the point of can be measured.

In FIG. 3, the probe complex 10 further has a probe holder 18.
The probe holder 18 has an inner surface 18a that is in close contact with the outer surface 1a of the propellant tank 1, and a plurality of openings for fixing the transmission probe 12, the reception probe 14, and the wedge member 16 to the above-mentioned positions. Has 18b and.
Each opening 18b is a hole penetrating to the inner surface 18a, and positions the transmission probe 12 and the wedge member 16 in close contact with the outer surface 1a of the propellant tank 1.
By using the probe holder 18, the relative positioning of the transmission probe 12, the reception probe 14, and the wedge member 16 can be easily performed.

Due to the configuration of the probe complex 10 described above, the receiving probe 14 is located away from the transmitting probe 12 along the outer surface 1a of the propellant tank 1. Therefore, even when the propellant thickness h is small, the time difference T between the transmission of the ultrasonic wave 5 and the reception of the reflected wave 5b becomes large, the influence of noise is reduced, and the time difference T can be easily measured.

FIG. 5 is an explanatory diagram of a method for measuring the liquid level shape of the propellant tank 1 according to the present invention.
Using the liquid level shape measuring device 100 described above, the liquid level shape measuring method of the propellant tank 1 according to the present invention comprises each step (step) of S1 to S3.
In step S1, a plurality of probe complexes 10 are fixed to the outer surface 1a of the propellant tank 1 at intervals.
In step S2, a plurality of liquid level positions P on the propellant liquid surface are detected by using the plurality of reflected waves 5b received by the plurality of receiving probes 14 of each probe complex 10.
In step S3, the shape of the propellant liquid surface 3a having a plurality of liquid level positions P on the propellant liquid surface is calculated.

According to the liquid level shape measuring method of the present invention, since the plurality of receiving probes 14 receive the plurality of reflected waves 5b, the reflected positions of the reflected waves 5b on the propellant liquid surface 3a are different. Therefore, even when the liquid surface shape fluctuates to various shapes, any of the reflected waves 5b can be detected by the plurality of receiving probes 14 in step S2.
Further, since the shape of the propellant liquid surface 3a is calculated in step S3, the propellant amount can be accurately calculated from the obtained shape of the propellant liquid surface 3a.

For example, when the propellant liquid level 3a floats in a sphere without touching the inner surface of the tank in the propellant tank, the size of the sphere is calculated from the liquid level positions of three or more points to accurately calculate the propellant amount. can do.
Also, if the liquid level shape is known as a set of arbitrary points when the propellant touches the inner surface, the shape of the propellant tank is known, so the propellant thickness is measured from the liquid level shape and integrated to determine the propellant amount. Can be calculated.

Therefore, according to the present invention, the propellant amount can be accurately measured in a weightless state, a state in which the acceleration direction changes, and a state in which the propellant remaining amount is small.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

C sound velocity, h propellant thickness, hm planned propellant thickness, P liquid level position, T time difference,
φ effective directivity angle, 1 propellant tank, 1a outer surface, 2 ultrasonic probe,
3 Liquid propellant, 3a propellant liquid level, 4 internal gas, 5 ultrasonic waves,
5a transmit wave, 5b reflected wave, 10 probe complex, 12 transmit probe,
14 receiving probe, 16 wedge member, 18 probe holder,
18a inner surface, 18b opening, 20 arithmetic unit, 100 liquid level shape measuring device

Claims (5)

It is a liquid level shape measuring device for a propellant tank that holds a liquid propellant inside.
A plurality of liquids on the propellant liquid surface due to a plurality of time differences between a probe complex fixed to the outer surface of the propellant tank and a plurality of time differences from the transmission of ultrasonic waves by the probe complex to the reception of the reflected wave of the ultrasonic waves. Equipped with an arithmetic unit that detects the surface position,
The probe complex includes a transmission probe that emits ultrasonic waves and a transmission probe that emits ultrasonic waves.
A liquid level shape measuring device for a propellant tank, comprising a plurality of receiving probes that surround the transmitting probe and are fixed to each other at a distance from each other to receive the reflected wave. Between the outer surface and the receiving probe of the propellant tank, it has a wedge member,
According to claim 1, the wedge member converts the incident angle of the reflected wave at the planned thrust thickness, which is the minimum detectable value of the thrust member, into a refraction angle suitable for the reception probe. The liquid level shape measuring device for the propellant tank described. The transmission probe has an effective directivity angle with respect to the sound axis of the ultrasonic wave to be transmitted.
The propellant according to claim 1, wherein the receiving probe is located at a position where the reflected wave can be received when the propellant liquid surface approaches the transmitting probe with a predetermined propellant thickness. Liquid level shape measuring device for tanks. The liquid in the propellant tank according to claim 2, further comprising a probe holder having an inner surface in close contact with the outer surface of the propellant tank and a plurality of openings for positioning the transmission probe and the wedge member. Surface shape measuring device. A method for measuring the liquid level shape of a propellant tank using the liquid level shape measuring device according to claim 1.
(A) A plurality of the probe complexes are fixed to the outer surface of the propellant tank at intervals from each other.
(B) Using the plurality of reflected waves received by the plurality of receiving probes of each probe complex, a plurality of liquid level positions on the propellant liquid surface are detected.
(C) A method for measuring the liquid level shape of a propellant tank, which calculates the shape of the propellant liquid level having a plurality of the liquid level positions.

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